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European Unconventional Resources
Technology of Production from Shale
Doug Bentley, European Unconventional, Schlumberger
May 29th, 2012Johannesburg, South Africa
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What are Unconventional Reservoirs
– Shale both Gas & Oil– Coal Bed Methane - CBM– Tight Gas– Gas Hydrates
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§ Organic Rich Shale§ Source Rocks§ Surrounding poor quality rock
ignored as non economic in the past.§ Porosity sources are mostly
unconventional§ Matrix Rock has Very Low
Permeability§ Require Hydraulic Stimulation to
make productive
What are Shale Reservoirs
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Shale Exploration - Starting Point
Petroleum Systems Modeling
Mosca et al. (2010) 3D Petroleum Systems modeling applied to unconventional shale gas play: prediction of sweet spots based on areal and depth distribution of sorption capacity in shale gas. Abstract AAPG Annual Convention and Exhibition, New Orleans, April, 2010.
Devon Energy have used Petroleum Systems Modeling to build their acreage position in a North American shale gas play:
•“Modeled variability of the gas adsorption and saturation thresholds as a function of temperature, maturity, and kinetic scheme through space and time by means of a 3D numerical simulation of hydrocarbon generation and expulsion”
•“Based on these results it was possible to select sweet spot locations to be leased for this project, consequently minimizing the lease and exploration costs”
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Reservoir Quality§ Maturity§ Organic Content§ Porosity§ Permeability§ Water Saturation§ Pressure§ Gas in Place
Completion Quality§ Stress Anisotropy § Fracture Containment§ Near & Far Field Stress§ Clay Content & Type§ Fabric Pattern§ Mineral Sensitivity§ Wellbore Placement
Understanding Reservoir & Completion Quality
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Shale Gas Reservoir Quality - Maturity Control – Petrology Tectonic subsidence (burial depth timing)Diagenesis (cements, clay, organics)
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Shale Gas Reservoir Quality – Organic Content & Porosity
Conventional sandstone
700 µm Pore system
Mineral framework Gas shale
100 µmFree gas in pore space Free gas in pore space
Adsorbed gas on kerogen
Kerogen
European Unconventional Resources0 6000 8000 10000
0
200
400
600
800
1000
0
200000
400000
600000
800000
1E+006
1.2E+006
1.4E+006
1.6E+006
1.8E+006
2E+006
Cumulative Time
Wel
l GA
S P
rodu
ctio
n R
ate,
Msc
f/d
Wel
l GA
S C
umul
ativ
eP
rodu
ctio
n, M
scf
Km = 0.0001 md
Km = 0.0005 md
Shale Gas Reservoir Quality – Permeability
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R² = 0.7254
0
100
200
300
400
500
600
0 10 20 30 40 50 60
Perm
(nD)
Sw
Shale Gas Reservoir Quality – Saturation
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Shale Gas Reservoir – Parameter RangesA-R Bulk Density
A-R Grain Density
Dry Grain Density Porosity Water
SaturationGas
SaturationMobile Oil Saturation
Gas-Filled
Porosity
Bound Hydrocarbon
Saturation
Bound Clay
Water
Pressure Decay Perm
TOC
(g/cm3) (g/cm3) (g/cm3) (% of BV) (% of PV) (% of PV) (% of PV) (% of BV) (% of BV) (% of BV) (md) (wt %)1 2.48 2.622 2.645 6.65 15.16 81.4 3.43 5.42 0.5 6.21 0.00027 3.772 2.436 2.559 2.584 6.26 18.5 76.44 5.05 4.79 1.29 7.03 0.00023 6.753 2.48 2.633 2.652 6.87 15.43 83.9 0.66 5.77 0.5 6.8 0.00027 3.364 2.327 2.487 2.509 7.74 13.09 83.02 3.87 6.43 0.73 6.67 0.000347 7.415 2.373 2.539 2.558 7.58 11.17 85.92 2.9 6.52 0.34 2.63 0.000359 5.956 2.461 2.605 2.63 6.87 16.26 80.42 3.32 5.53 0.99 7.19 0.000298 5.047 2.75 2.812 2.818 2.48 7.41 88.89 3.69 2.21 0.29 1.87 0.000044 0.988 2.341 2.511 2.527 7.66 7.67 88.39 3.93 6.77 0.82 4.9 0.000463 7.849 2.428 2.573 2.599 7.11 17.77 79.06 3.16 5.62 0.75 7.01 0.000292 4.12
10 2.468 2.633 2.645 6.87 5.5 91.15 3.34 6.26 0.91 4.58 0.000305 4.0211 2.525 2.593 2.661 6.53 54.54 40.42 5.03 2.64 0.1 5.19 0.000112 2.2912 2.637 2.73 2.765 5.27 34.63 64.44 0.92 3.4 0.05 5.04 0.000149 613 2.451 2.543 2.599 6.97 47.77 51.58 0.64 3.6 0.28 9.45 0.000161 5.314 2.432 2.574 2.605 7.29 24.19 75.19 0.61 5.48 0.28 7.48 0.000333 5.7315 2.436 2.56 2.579 5.96 18.23 81.01 0.75 4.83 0.28 5.05 0.000346 6.5916 2.445 2.548 2.573 5.38 9.65 75.13 15.21 4.05 0.4 3.12 0.000243 5.1917 2.523 2.619 2.687 7.02 9.07 51.88 39.04 3.65 0.67 3.22 0.000176 5.6818 2.472 2.606 2.621 5.99 13.06 85.56 1.37 5.13 0.25 4.76 0.000325 6.26
Sample No
�Saturations: Sliquid < 45%�Permeability: > 100 nD� TOC: > 2 wt%
�Effective phi: 4 to ~12 pu
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Shale Gas Reservoir – Pressure Measurement
Pumpout module
Packer
Wireline
Packer
Pressure gage
Flow control module
Sliding coupling
P
P
Inflate seal valve
Interval seal valve 1m
Sample chamber
P
3ft
0 60.0 120.0 180.0 240.0 300.0 360.0 420.0 480.0 540.0 600.00
1000
2000
3000
4000
5000
6000
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50Interval Pressure (psi)
Packer Pressure (psi)
Injection Rate (gal/min)
Time, min
Pres
sure
, psi R
ate, gpm
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Shale Gas Reservoir – Pressure MeasurementEight Hour Shut-in
35 psi
§ Run Sensitivity during Closure§ Estimate pressure at 0.453 psi/ft§ Gradient used to estimate Gas in
Place, assuming Saturated System
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Shale Gas Reservoir – Gas in Place
0
20
40
60
80
100
120
140
0 200 400 600 800 1,000 1,200Pressure, psia
Adso
rbed
Gas
Con
tent
, scf
/ton
Total Organic Carbon= 16 %
14 %
12 %
10 %
8 %
6 %
4 %
Methane Adsorption Isotherms(as a function of Total Organic Carbon)
§ Gas in Place Calculated from CBM Standard BCF per Sq Mile§ TOC is considered Saturated for
most cases as we are well over 1000 psi in most wells.§ Effective porosity is used with
estimated pore pressure.§ Gas in Place is Integrated over total
Shale bottom to top of interval.§ Examples:§ Core Barnett 139 BCF/ Sq Mile§ Marcellus 60 BCF/Sq Mile§ Haynesville 129 BCF/Sq Mile
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ECS / XRDRHOBRHOM
SwPorosity
TOCPermPorosity
GIPGas-PhiELANResistivityGR
Shale Gas – Core Calibrated Reservoir Quality
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Shale Gas Completion Quality – Mechanical Properties Shale can be very anisotropic due to laminations and bedding(especially expandable clays or organic)§ TIV – Transverse Isotropic with Vertical axis of
symmetry
Shale, laminated sands
Comp.VerticalVelocity
Comp.HorizontalVelocity
Not the Same!!
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Shale Gas Completion Quality – Anisotropic Properties
16
FastStrong
Slow Weak
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Shale Gas Completion Quality – Anisotropic Stress
Argillaceous Shale BedEh = 6 x 106 psiEv = 3 x 106 psi
νh = 0.26νv = 0.25
Overburden
Siliceous Shale Bed Eh = 8 x 106 psiEv = 6 x 106 psi
νh = 0.16νv = 0.13
Argillaceous Shale:Isotropic: σh = 0.66 psi/ft Anisotropic: σh = 0.87 psi/ft
Siliceous Shale:Isotropic: σh = 0.53 psi/ftAnisotropic: σh = 0.57 psi/ft
Anisotropic shale properties increases stress in argillaceous intervals
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Shale Gas Completion Quality – Fracture Containment Mineralogy
Closure StressφD & φNRes.GR
Isotropic & Anisotropic
Closure Stress
Swelling Clays = High Closure Stress
High Silica Volume = Low Closure Stress
Carbonates my be High or Low Closure Stress
High Clay Volume = High Closure Stress
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Shale Gas Completion Quality – Clay Volume
- Good relationship between theclay volume and the differencebetween the Anisotropic andIsotropic closure stress models
- Correlation is weakest at lowclay volumes where therocks are more isotropic
- Increasing the clay volumeincreases the error in theisotropic stress model
Tota
l Clay
Vol
ume
Difference in Anisotropic and Isotropic Stresses
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Shale Gas Completion Quality – Clay Type
- Excellent relationship betweenthe volume of swelling clay and the difference between theAnisotropic and Isotropicclosure stress models
- Small amounts of swellingclays dramatically increaseclosure stress
- Not captured withIsotropic models
Swell
ing
Clay
Vol
ume
Difference in Anisotropic and Isotropic Stresses
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Shale Gas Completion Quality – Role of Fabric• Rock fabric can be very complex • Fractures can be open, healed, drilling induced or reactivated• Clay is usually found in layers• Mud systems need to limit activation of healed systems• All planes of weakness need to be mapped• Regional stress needs to be understood
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Shale Gas Completion Quality – Creating Surface Area
Complex Hydraulic Fracture Simulations
3D Stress Mapping
Creating Productive Surface Area
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Shale Gas Completion Quality – Maintaining Surface Area 20/40 Resin Coated Sand Argillaceous Facies
20/40 Sand Siliceous Facies
Post-Conductivity Testing Fracture Face Image
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Shale Gas Completion Quality – Maintaining Surface Area Results of Channel Fracturing•Reductions in water of 25% and proppant of 42% •Production: 20-50% increase
•Proppant placement rate: 99.96%
Key elements• Improved fracture clean-up
• Low risk of screenout
• Longer effective fracture half-lengths
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Shale Gas Completion Quality – Well Placement 4100
4200
4300
4400
4500
4600
47003000 3500 4000 4500
TVD
- ft
Stress - ps i
-0.10 -0.05 0.00 0.05 0.10
Width at Wellbore - in @115.4 min
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Fracture Half Length - f t @115.4 min
Frac Half Length Propped Frac Half Length4100
4200
4300
4400
4500
4600
47003000 3500 4000 4500
TVD
- ft
Stress - ps i
-0.10 -0.05 0.00 0.05 0.10
Width at Wellbore - in @115.4 min
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Fracture Half Length - f t @115.4 min
Frac Half Length Propped Frac Half Length4100
4200
4300
4400
4500
4600
47003000 3500 4000 4500
TVD
- ft
Stress - ps i
-0.10 -0.05 0.00 0.05 0.10
Width at Wellbore - in @115.4 min
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Fracture Half Length - f t @115.4 min
Frac Half Length Propped Frac Half Length
Upper Shale
Lower Shale
Lower Boundary
Argillaceous Lower Shale
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Shale is heterogeneous at all scalesReservoir Quality and Completion Quality can be defined.Data integration is used to define and exploit the reservoir.Production improvements come from many things
• Well placement where conductivity to the developed fracture system can be developed and maintained.• Large surface area contained in the reservoir.• Propprant concentrations placed to maintain surface area and minimize pinch points in the reservoir.• Water flowback program to minimize reservoir damage and fines production.• Stimulation fluids program to limit Chemo-mechanical weathering.
Reservoir & Completion Quality - Summary